I guess the main confusion of defining this lens is probably the setting of depth/frequency. h;^H*Y&`
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The main fresnel lens types are: L=7 U#Q/DE
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* Constant groove depth. dKOW5\H'
* Contant groove pitch types. .3{PgrZ
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So if your depth is fixed you will define +ve value in the cell and to specify the "height" or "depth" of each groove feature. If the frequency of the groove is fixed then you use -ve value. Say putting down - 5 this implies that there are 5 grooves with a unit length. u9 t@%H)lZ
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Hope this helps!!
